Gamma-valerolactone (GVL, 5-methylbutyrolactone) is a valuable compound which can be used in the production of adipic acid (1,6-hexanedioic acid) which is an important precursor for inter alia the production of polyamides such as polyamide 6,6 or polyamide 4,6 (also referred to as “Stanyl”). Hydrogenation of levulinic acid to produce GVL is described in L. E. Manzer, Appl. Catal. A, 2004, 272, 249-256; J. P. Lange, J. Z. Vestering and R. J. Haan, Chem. Commun., 2007, 3488-3490; R. A. Bourne, J. G. Stevens, J. Ke and M. Poliakoff, Chem. Commun., 2007, 4632-4634; H. S. Broadbent, G. C. Campbell, W. J. Bartley and J. H. Johnson, J. Org. Chem., 1959, 24, 1847-1854; R. V. Christian, H. D. Brown and R. M. Hixon, J. Am. Chem. Soc., 1947, 69, 1961-1963; L. P. Kyrides and J. K. Craver, U.S. Pat. No. 2,368,366, 1945; H. A. Schuette and R. W. Thomas, J. Am. Chem. Soc., 1930, 52, 3010-30121; WO2012/175439; US2006/0100449; and US2003/0055270.